The present invention relates to a damping resin composition, and a damping resin article for a structure formed from the damping resin. In particular, the present invention is concerned with a damping resin composition suitably used for forming parts surrounding the engine, for example, a rocker cover, a gear case cover, and an oil pan, and other parts, such as a noise cover, that are required to have a high damping capability, and such a damping resin article that is formed from the resin composition.
In recent years, the movements for conservation of resources and reduced pollution have been prevailing in view of global environmental protection, and, in particular, it has been strongly demanded to reduce or prevent pollution in transportation fields such as automobiles, ships, airplanes, and trains. To this end, reduction in the weight of vehicles and improvement in the fuel economy have been widely studied.
As one method of reducing the weight of a motor vehicle, for example, it has been proposed to form various components from a resin material. Resin articles posses more excellent characteristics, such as higher freedom in choice of design, lighter weight, and higher specific strength, as compared with metal articles. Among known resin compositions, FRP (Fiber Reinforced Plastic), whose strength and weight can be easily balanced with each other, has been widely used for forming outer plates, interior materials, and engine surrounding parts of automobiles, for example. In particular, parts that constitute or surround the engine are required to be light in weight, and also exhibit a high damping capability to meet with a high demand for reduced noise.
The damping characteristics of resin materials can be effectively enhanced by increasing the loss tangent (Tan xcex4) of dynamic distribution due to an increase in the loss elastic modulus and a reduction in the storage elastic modulus at around the glass transition temperature of the resin composition. Thus, the loss tangent (Tan xcex4) of the resin material has an influence on the damping characteristic thereof. Here, the loss tangent (Tan xcex4) is expressed as the ratio of the loss elastic modulus (Exe2x80x3) to the storage elastic modulus (Exe2x80x2), i.e., Tan xcex4=Exe2x80x3/Exe2x80x2.
As known damping resin compositions for use in the engine, laid-open Japanese Patent Publications Nos. 3-137158 and 3-137159 disclose damping resin compositions containing nylon, or the like, as a basic material, for example.
When the damping resin compositions containing nylon as disclosed in the above-identified publications are used for forming large-sized articles, however, the articles are likely to suffer from warpage and deformation due to relatively low rigidity of the material.
In the meantime, laid-open Japanese Patent Publication No. 8-301998 discloses a damping resin composition called a sheet molding compound (hereinafter referred to as xe2x80x9cSMCxe2x80x9d).
The SMC disclosed in the above-identified publication exhibits a good damping characteristic under a high-temperature atmosphere, causing no problem in practical use, but the damping characteristic may deteriorate under a low-temperature atmosphere upon the start of the engine, for example.
It is, therefore, an object of the present invention to provide a damping resin composition having an improved damping characteristic over a wide range of temperatures and also having an excellent molding or shaping characteristic, and a damping resin article for a structure formed from the resin composition.
To accomplish the above object, the present invention provides a damping resin composition comprising bifunctional diacrylate or bifunctional dimethacrylate (A) expressed by the formula (1) below, and an unsaturated polyester resin (B+C) consisting of unsaturated polyester (B) and a cross-linking monomer (C), wherein the component (A) is contained in an amount of 15 to 85% by weight, and the component (B+C) is contained in an amount of 85 to 15% by weight.
CH2=CR2COxe2x88x92(R1O)nxe2x88x92OCOCR2=CH2xe2x80x83xe2x80x83(1)
where n is integer equal to or greater than 2, R1 is an alkylene or polymethylene chain having 2 to 13 carbon atoms, and R2 is hydrogen or a methyl group.
The present invention also provides a damping resin composition comprising bifunctional diacrylate or bifunctional dimethacrylate (A) expressed by the formula (1) above, and an epoxy acrylate resin (Bxe2x80x2+C) consisting of epoxy acrylate (Bxe2x80x2) and a cross-linking monomer (C), wherein the component (A) is contained in an amount of 15 to 85% by weight, and the component (Bxe2x80x2+C) is contained in an amount of 85 to 15% by weight.
The present invention also provides a damping resin composition comprising bifunctional diacrylate or bifunctional dimethacrylate (A) expressed by the formula (1) above, an unsaturated polyester resin (B+C) consisting of unsaturated polyester (B) and a cross-linking monomer (C), and an epoxy acrylate resin (Bxe2x80x2+C) consisting of epoxy acrylate (Bxe2x80x2) and a cross-linking monomer (C), wherein a component (Bxe2x80x3+C) contains the component (B+C) in an amount of 5 to 95% by weight and the component (Bxe2x80x2+C) in an amount of 95 to 5% by weight, and the resin composition contains the component (A) in an amount of 15 to 85% by weight and the component (Bxe2x80x3+C) in an amount of 85 to 15% by weight.
Each of the damping resin compositions as indicated above may further contain a filler (E), a curing agent (F), a mold releasing agent (G), and a shrinkage reducing agent (H), and a thickener (I). A reinforcing material (J) composed of glass fibers, or the like, may be impregnated with the resin compound containing these agents as well as the above components (A), (B+C) and/or (Bxe2x80x2+C), and the resulting resin composition is aged and thus formed into the shape of a sheet or a bulk. In this manner, a damping resin article for a structure is formed of the damping resin composition.
The resin composition provided according to the present invention exhibits a high damping capability over a wide range of temperatures, while assuring a good molding characteristic, and the damping resin article for a structure using this resin composition also exhibits a high damping capability.